1. Field of the Invention
The present invention relates generally to a magnetic head, and more particularly, to a magnetic head for recording and reproducing data in a state in which the magnetic head floats over a rotating recording medium, that is, a rotating magnetic disk, due to a change in air flow arising between the magnetic head and the magnetic disk.
2. Description of the Related Art
Generally, an ordinary magnetic disk drive that uses a flexible magnetic disk having a coercive force of 900 oersted (Oe) or less as a magnetic recording medium allows a relatively low rotational speed of for example 300 rpm. In this case, magnetic recording and reproduction is performed by causing the magnetic head to be in direct sliding contact with the magnetic disk.
However, with advances in recent years in high-density recording on magnetic disks, the rotation speed of the magnetic disk has been increased to for example 3000 rpm, with the coercive force of the magnetic disk being increased to 1500 Oe or more. As a result, in order to accommodate such so-called high-capacity magnetic disks a magnetic disk drive has appeared in which the magnetic head is provided with a narrow gap. Hereinafter such a magnetic disk drive will be referred to as a high-capacity magnetic disk drive.
Since a high-capacity magnetic disk drive allows the magnetic disk to be rotated at high speeds, the magnetic disk and the magnetic head used therein may be easily damaged if the magnetic head were to be caused to be in direct contact with the magnetic disk, as is done in the conventional magnetic disk drive.
As a result, the high-capacity magnetic disk drive is designed so that the magnetic head floats in an elevated state over the surface of the high-capacity magnetic disk due to an elevating force arising as a result of a change in an air flow caused by a relative speed between a slider surface of the magnetic head and the magnetic disk. Magnetic recording and reproduction is performed while a state of non-contact between the magnetic head and the magnetic disk is maintained.
FIGS. 1, 2, 3, 4 and 5 show a magnetic head used in the conventional high-capacity magnetic disk drive. As shown in FIGS. 1 and 2, the conventional high-capacity magnetic head 1 generally comprises a slider 2 and a magnetic head unit 3. The slider 2 supports the magnetic head unit 3 and causes the magnetic head unit 3 to float over the magnetic disk 6.
The top surface of the slider 2 forms an air bearing surface for forming an air bearing with respect to the magnetic disk 6. Additionally, a central groove 2a is formed at a central position of the top surface of the slider 2. As shown in FIG. 1, the central groove 2a divides the air bearing surface into a first air bearing surface 2b located to the right side of the central groove 2a and a second air bearing surface 5 located to the left side.
The magnetic head magnetic head unit 3 and a pair of grooves or slots 4 are provided at the first air bearing surface 2b. The magnetic head unit 3 for performing magnetic recording and reproducing is formed by sandwiching a gap member between thin plates of magnetic cores.
The slots 4 extend in a tangential direction of the magnetic disk 6, that is, in the direction of arrow X in FIG. 1, and provide a vent for an air flow produced between the magnetic disk 6 and the first air bearing surface 2b. By providing a vent to the air flow produced between the magnetic disk 6 and the first air bearing surface 2b, an elevating force exerted on the magnetic head 1 is reduced. Accordingly, by providing the slots 4, the elevating force of the magnetic head 1 can be controlled.
As described above, the second air bearing surface 5 is formed to the left of the central groove 2a located on the top surface of the slider 2 as shown in FIG. 2. Like the first air bearing surface 2b, the second air bearing surface 5 also produces a force for elevating the magnetic head 1.
FIG. 3 is a lateral cross-sectional view from a radial direction of disk approach. As shown in the drawing, a pair of magnetic heads are supported so as to be opposite each other within the magnetic disk drive. The elevating force generated by the second air bearing surface 5 described above exerts a force that pushes the magnetic disk 6 in the direction of the first air bearing surface 2b, that is, in the direction of the magnetic head unit 3, of the opposite magnetic head 1. Accordingly, the second air bearing surface 5 also functions as a pressure pad for pressing the magnetic disk 6 toward the opposite magnetic head 1.
Additionally, as described above slots 4 are formed in the first air bearing surface 2b. The slots 4 provide a vent for the air flow produced between the magnetic disk 6 and the fist air bearing surface 2b, thus reducing the elevating force exerted on the magnetic head 1. Accordingly, the magnetic disk 6 is deformed by a negative pressure generated in the slots 4 and a pressure generated at the second air bearing surface 5 due to a change in air flow so as to warp toward a gap 3a as the magnetic disk 6 rotates between the pair of magnetic heads 1. With this construction, optimum recording to and reproduction from the magnetic disk 6 is ensured even with floating magnetic heads 1.
A description will now be given of how the magnetic heads 1 face the magnetic disk 6, with reference to FIG. 4 and FIG. 5. FIGS. 4 and 5 show views of a state in which the magnetic head 1 is recording to or reproducing from a magnetic disk 6, from a radial Y direction of the magnetic disk 6.
FIG. 4 shows the magnetic disk 6 in a state of optimal approach to the magnetic head 1.
As shown in FIG. 4, a pair of slots 4 are formed in the first air bearing surface 2b in which the first magnetic head unit 3 is provided. These slots 4 are formed along an entire length of the first air bearing surface, that is, a direction indicated in the drawing by the double-headed arrow X, from a leading edge 7 of the magnetic head 1, that is, an edge side of the magnetic head 1 at which the magnetic disk 6 enters the magnetic head 1, to a trailing edge 8 of the magnetic head 1, that is, an edge side of the magnetic head 1 at which the magnetic disk 6 exits the magnetic head 1. As a result, a reduction in the elevating force due to the presence of the slots 4 is generated over the entire extent of the length of the first air bearing surface 2b.
Accordingly, even in a state of optimal approach a distance H between the magnetic disk 6 and the leading edge 7 of the magnetic head 1 in the above-described construction in which the slots 4 are provided is smaller than a corresponding distance in a construction in which the slots 4 are not provided.
Moreover, with such a construction the magnetic disk 6 is maintained in close proximity to the magnetic head unit 3 as a result of the reduction in elevating force by the slots 4, thus providing optimal magnetic recording and reproduction.
By contrast, FIG. 5 shows a state in which the magnetic disk 6 approaches the magnetic head 1 at a height position lower than that of an optimal approach. Such a small-clearance state of approach results from the flexibility of the magnetic disk 6 or from inevitable errors in the production process thereof.
When the height of the magnetic disk 6 upon approach to the magnetic head 1 is lower than a standard optimum height position as described above, the distance H is reduced to such an extent that the magnetic disk 6 may come into contact with the leading edge 7 of the magnetic head 1, and the magnetic disk 6 or the leading edge 7 of the magnetic head 1 may be damaged as a result.
At the same time, although the magnetic disk 6 is ordinarily enclosed in a hard case so as to prevent particles of dirt and dust from adhering to the surface of the magnetic disk 6, it is impossible to completely prevent the attachment of dust thereto, with the result that, inevitably, dust collects on the surface of the magnetic disk 6. If magnetic recording to and reproducing from a magnetic disk 6 to the surface of which dust has adhered is performed using a magnetic head 1, the dust may break loose from the surface of the magnetic disk 6 by the air flow generated at the first and second air bearing surfaces 2b, 5 and adhere to the magnetic heads 1.
As a result, because the width dimension of the slots 4 In the conventional magnetic head 1 is small the flow of air is restricted and thus dust accumulates in the slots 4. If this accumulated dust then breaks loose from the first and second air bearing surfaces 2b, 5, the magnetic disk 6, which is rotating at high speed, may be damaged by collision with the dust or the flow of air may be impaired by the dust, thus impairing proper magnetic recording and reproduction.
Further, the conventional magnetic head 1 has an overall box-like shape and a relatively heavy structure. As a result, the magnetic head 1 is unable to track the magnetic disk 6 if the magnetic disk 6 oscillates in a state in which the magnetic head 1 floats over the magnetic disk 6 to perform magnetic recording and reproduction. Thus, the magnetic head 1 and the disk 6 collide.
In other words, because the magnetic disk 6 is a flexible disk the magnetic disk 6 inevitably oscillates as the magnetic disk 6 rotates. At the same time, because the magnetic head 1 is heavy a large inertial force is exerted on the magnetic head 1. In the event that the magnetic disk 6 is displaced due to rotational oscillation, the large size of the inertial force prevents the magnetic head 1 from displacing instantaneously and thus the magnetic head 1 cannot follow the rotational oscillation of the magnetic disk 6. Accordingly, with the conventional magnetic head 1 it sometimes happened that the magnetic head 1 and the magnetic disk 6 collided when the magnetic disk 6 began to oscillate.